Coal and biomass hydrolysis, in which a portion of coal and/or biomass is converted into a series of useful, high caloric gases, was first developed as early as the eighteenth century. However, commercial conversion to liquid or gas became more widespread in the early to mid 1900's. Intense renewed interest in pyrolysis to upgrade a variety of raw coals was spurred by the tensions between the West and the oil rich nations of the Middle Eastern countries in the 1970's. In general, depending on the nature of the raw coal and/or biomass in addition to the exact nature of the pyrolysis process, the gas and char from coal and biomass pyrolysis generally contains water vapor, and compounds of chlorine, mercury, additional heavy metals, hydrogen sulfide, and a range of hydrocarbon volatiles. Any solid, non-volatized coal char will contain carbon, a range of hydrocarbon compounds, and traces of other minerals and elemental compounds. The volatized gases can be separated and the individual gaseous products can be further processed for useful chemical applications. At the same time, burning coals and biomass that have been properly pyrolyzed, reduces air pollutions and hence human health hazards such as emphysema, asthma, and lung cancer. The large number of issued patents involving pyrolysis, liquefaction or gasification of coal gives a broad picture of the utility and profitability of the conversion of coal to achieve a cleaner hydrocarbon fuel.
The history and detailed time-line of coal pyrolysis are well documented and found on a variety of websites. Details of a pyrolysis process can be found, for example, in “Kinetic Studies of Gas Evolution During Pyrolysis of Sub-bituminous Coal,” by J. H. Campbell et al., a paper published May 11, 1976 at the Lawrence Livermore Laboratory, Livermore, Calif. Numerous issued U.S. patents describe methods for the reduction of sulfur in coal, for example, U.S. Pat. No. 7,056,359 by Somerville et al. Their process involves grinding coal to a small particle size, then blending the ground coal with hydrated lime and water, followed by drying the blend at 300-400 degrees F. U.S. Pat. No. 5,037,450 by Keener et al. utilizes a unique pyrolysis process for denitrifying and desulfurizing coal. Here the sulfur and nitrogen content of coal is again driven off in gaseous form and sequestered for possible further use.
Related art is described in U.S. Pat. No. 4,862,485, which teaches means for forming coal pellets by mixing coal particles with polyvinyl alcohol, calcium oxide and/or magnesium oxide and water. U.S. Pat. No. 4,738,685 teaches how to cold press coal fines with molasses, an inorganic hardening agent such as calcium carbonate, calcium phosphate, iron oxide, aluminum oxide and optionally with an acid. Additional teachings relevant, though differing from the present application can be found in U.S. Pat. Nos. 4,618,347, 4,586,936, 4,169,711 and 5,916,826. Patent application No. 20100162619 describes a method using a Mallard process at a pressure of 5 bar at an elevated temperature for compacting biofuels together with some limited amount of peat or lignite.
A more recent system has been proposed and published as USPTO application 20090020456 (Jan. 22, 2009) by Tsangaris et al, relating to the gasification of fossil fuels, fuels which are then used to process a variety of unconventional sources of oil sources such as tar sands and shale oil.
The present application describes unique and novel systems and methods for obtaining calorically rich combustibles, nearly contaminant free combustibles for gasification consisting of coal and biomass. The invention involves the preprocessing of the coal and biomass so resulting in major energy saving during the gasification stage. The biomass can consist of algae, switch grass, wood matter, such as sawdust and/or wood chips, as well as manure to mention a non-exhaustive number of useful caloric components.
One of the several ways the present invention is particularly efficient is that it greatly reduces the water vapor that is released from coal and biomass upon heating in a typical kiln. The fuel to be gasified which has already had the water removed makes the gasification considerably more efficient. At the same time, other contaminants such as S, H2S, Cl, Hg and several heavy metals which have also been removed prior to gasification increases the efficiency and quality of the gasification process. Some of these pollutants can then be reprocessed for further useful applications. This form of waste management is becoming recognized world wide as a necessary and achievable goal to reduce air pollution and potential global warming.
While some of the waste products from the burning of fossil fuels and biomass can be-recovered or recycled, most are disposed of in landfill. This type of disposal is wasteful and in itself potentially polluting, clearly not an environmentally friendly or economical way to proceed. Various government agencies have now put laws into effect that make certain forms of this type of disposal illegal which can result in substantial fines.